In the art of damper valves of the type used to control the flow of gas in a gas conducting flue such as the flue of a coal burning power plant it is well known to provide a purged damper for such purposes as bypassing a portion of the flue. For example in flue gas cleansing systems such as baghouse filters and the like purged bypass dampers have often been provided to connect a portion of the flue upstream from the filter with a portion of the flue downstream from the filter whereby the gas passing through the flue may be selectively caused to either bypass or pass through the filter by selective opening and closing of the bypass damper. Purging of such bypass dampers as by pressurized gas precludes any leakage of flue gas past the bypass damper when closed. Leakage is especially undesirable in flue gas filtering systems in that it permits dirty flue gas flowing in the upstream flue portion to leak over into the clean gas stream flowing in the downstream portion of the flue thus reducing overall filter operating efficiency and system reliability.
Although prior purged dampers have generally served their intended purposes they have nevertheless often been subject to troublesome deficiencies. For example, prior dampers such as the guillotine or butterfly types have often included a pair of spaced apart valve members rather than a single valve member and the operating mechanism for such dampers has often been rather more complex than that of a single valve member. The added need in such dampers for a conduit means to deliver purging gas thereto has further complicated prior bypass damper structures. Additionally, many prior purged dampers have not been well adapted for use in a valved passage comprised of an opening in a common wall between adjacent countercurrent flow flue portions.
The hereinabove cited deficiencies of prior purged dampers are overcome by the present invention according to which there is provided a gas purged poppet or domed head type damper valve which includes a pair of spaced apart domed disc-like valve heads. The operating mechanism of the damper of this invention is substantially no more complex than that of a single head poppet type valve, and the structure of the present invention may be further simplified by having the purge gas inlet means constructed integrally with the actuating mechanism of the damper. Furthermore, the damper of this invention is quite well suited for use either in an elongated duct or flue portion or in a valved gas flow passage comprised substantially of an opening in a common wall between separate flue or duct portions. The invention is particularly well suited to use in a bypass portion of a gas flue.